What is the recommended treatment for pylonephritis?

Treatment of Pyelonephritis

For outpatient treatment of uncomplicated pyelonephritis, use oral ciprofloxacin 500 mg twice daily for 7 days if local fluoroquinolone resistance is below 10%, or levofloxacin 750 mg once daily for 5 days as equally effective alternatives. 1, 2

Initial Diagnostic Steps

• Always obtain urine culture and susceptibility testing before initiating antibiotics to guide definitive therapy and avoid treatment failure from resistant organisms 1, 2
• The combination of leukocyte esterase and nitrite testing has 75-84% sensitivity and 82-98% specificity for urinary tract infection 3
• Urine cultures are positive in 90% of pyelonephritis cases 3
• Blood cultures should be reserved for immunocompromised patients, uncertain diagnoses, or suspected hematogenous infections—not routinely needed in uncomplicated cases 3, 4

Outpatient Treatment Algorithm

When Local Fluoroquinolone Resistance is <10%:

• First-line: Ciprofloxacin 500 mg orally twice daily for 7 days 1, 2, 5
  • Alternative: Ciprofloxacin 1000 mg extended-release once daily for 7 days 1
  • Alternative: Levofloxacin 750 mg once daily for 5 days 1, 2, 6
• These fluoroquinolone regimens achieve 93-97% cure rates 2

When Local Fluoroquinolone Resistance is ≥10%:

• Give one initial IV dose of ceftriaxone 1g or an aminoglycoside, then start oral fluoroquinolone therapy 1, 7, 4
• This approach overcomes the problematic resistance rates while allowing outpatient management 4

If Pathogen is Known to be Susceptible:

• Trimethoprim-sulfamethoxazole 160/800 mg (double-strength) twice daily for 14 days 1, 2
  • Only use if documented susceptibility—do not use empirically due to high resistance rates 7, 4
• Oral cephalosporins for 10 days (less effective than fluoroquinolones) 2
  • Must give initial IV dose of long-acting parenteral antimicrobial first 2

Agents to Never Use for Pyelonephritis:

• Never use nitrofurantoin, oral fosfomycin, or pivmecillinam—insufficient data for upper urinary tract infections 2
• Oral β-lactams as monotherapy without initial parenteral dose are inadequate 1

Inpatient Treatment Algorithm

Indications for Hospitalization:

• Complicated infections, sepsis, persistent vomiting, failed outpatient treatment, extremes of age, or pregnancy 3, 4
• Pregnant patients require admission due to significantly elevated risk of severe complications 4

Initial IV Antibiotic Regimens:

• Fluoroquinolone (levofloxacin 750 mg IV daily) 1, 8
• Aminoglycoside with or without ampicillin (gentamicin 5-7 mg/kg once daily) 1
• Extended-spectrum cephalosporin (ceftriaxone 1g IV every 12 hours) 1, 8
• Extended-spectrum penicillin with or without aminoglycoside 1
• Carbapenem (for suspected extended-spectrum beta-lactamase producers or sepsis) 1, 4

Transition to Oral Therapy:

• Switch to oral antibiotics when clinically improved (typically 48-72 hours) 4
• Total treatment duration: 10-14 days for β-lactams, 5-7 days for fluoroquinolones, 14 days for TMP-SMX 1, 2

Treatment Duration by Agent

• Fluoroquinolones: 5-7 days depending on specific agent and dose 1, 2
  • Levofloxacin 750 mg: 5 days 1, 6
  • Ciprofloxacin 500 mg: 7 days 1, 5
• Trimethoprim-sulfamethoxazole: 14 days 1, 2
• β-lactams: 10-14 days (even when transitioning from IV to oral) 1, 2

Microbiology Considerations

• Escherichia coli causes 75-95% of cases, with occasional Proteus mirabilis and Klebsiella pneumoniae 1, 3, 7
• High resistance rates exist for cotrimoxazole (55%), ciprofloxacin (48%), and ceftriaxone (34%) in some regions 8
• Tailor empirical therapy based on local resistance patterns and adjust according to culture results 1

Follow-up and Treatment Failure

• Repeat urine culture 1-2 weeks after completing antibiotics 3
• Most patients respond within 48-72 hours 4
• If no improvement by 48-72 hours: obtain repeat blood and urine cultures, consider imaging (contrast-enhanced CT), evaluate for resistant organisms, anatomic abnormalities, or obstruction 3, 4
• Concurrent urinary tract obstruction requires urgent decompression 4

Special Population: Elderly Patients

• Monitor closely for adverse effects, particularly with aminoglycosides and fluoroquinolones 1
• Ciprofloxacin for 7 days is effective and safe even in older women with more severe infections 5

Critical Pitfalls to Avoid

• Failing to obtain cultures before starting antibiotics prevents appropriate adjustment of therapy 1
• Using fluoroquinolones empirically in areas with >10% resistance without initial parenteral dose leads to treatment failure 1, 2
• Not adjusting therapy based on culture results perpetuates resistance and risks failure 1
• Inadequate treatment duration with β-lactams (must complete 10-14 days) 1
• Using oral β-lactams as monotherapy without initial parenteral dose 1